Wireless carriers may operate different types of communication networks. Some such networks may be optimized for voice services, while others may be optimized for providing data services.
Presently, 3rd Generation Partnership Project 2 (3GPP2) carriers (also known as CDMA2000 carriers) often operate a pair of networks. The first such network, referred to herein as 1xRTT, operates in accordance with the CDMA2000 1x standard (also known as International Standard 2000 (IS-2000)), and is optimized for voice services, Short Message Service (SMS) text messaging, and related services. The second such network, referred to herein as 1xEV, operates in accordance with the CDMA2000 1xEV-DO standard (also known as International Standard 856 (IS-856)), and is optimized for packet-oriented data services.
Some communications networks provide broadcast messaging services to facilitate transmitting a message to several mobile devices. One such service, the Commercial Mobile Alert Service (CMAS), also known as the Personal Localized Alerting Network (PLAN), enables the transmission of emergency alerts to CMAS-enabled mobile devices located in a geographically targeted area. In the United States, support for receiving CMAS alerts will, starting in early 2012, become a Federal Communications Commission (FCC) mandate for carrier networks and mobile devices. For mobile devices, the FCC mandate will require: that a mobile device cannot opt out of receiving alerts designated as being Presidential alerts, and that upon receiving a CMAS alert, a mobile device should play a tone and vibrate. For now at least, there is no FCC requirement for mobile devices regarding CMAS delivery success rates or latency.
CMAS alerts are expected to be sent only in case of emergency. Accordingly, there is no expectation that a carrier network will send CMAS messages at a certain time of the day. CMAS messages could be sent to mobile devices at any time. When CMAS messages are sent, timely delivery may be important to the user.
For 3GGP2 carriers (e.g. Verizon™ and Sprint™), CMAS alerts will be delivered as a broadcast SMS over a 1xRTT forward common channel, typically following a cycle defined by a broadcast index. When CMAS is enabled in a specific coverage area, a mobile station in that area will periodically tune to 1xRTT, typically at a time slot defined by the broadcast index (the broadcast slot), to receive the broadcast SMS.